I seem to have missed the release of this feature. I can't find any information on it in the rules, either. Could someone point me to the appropriate section of the rules, the GNS announcing its release/explanation, and/or explain it to me?

Specifically, I want to know what the new ship categories mean and how they differ from the old ones and how forming squadrons works and what ships can do it.

All ships can form squadrons, they just have differing amounts of squad size they take up, to a maximum of 12 for your party.

As for the categories, I'm not sure if it has been updated on the rules pages, but basically the first few to just before heavy haulers are capital skill ships, heavy haulers to fighters are fregither/fighter skill ships.

Theoretically, is it safe to assume that when the rules are fully implemented someone with a Space Command of 5 could control 5x12 slots + 12 slots for your squadron = 72 slots just like how Infantry Command skill works?

Could I then also assume that a Space Command 5 skill would allow you to control 6 Dreadnought class ships as long as they fit into the 72 combines slots?

...and yes I know rules can change but I am asking about intended usage of current rules that are not fully implemented.

Cool, thanks. I am sure I am not the first person to suggest this but we could say enormous ships like SSD's use up 60 slots or something like that but still allow a single character with a Space Command skill of 0 to fly it.

Theoretically it means you can only have one per squad, and the number of squads is contingent on space command skill, which is why these things will be reviewed before the space command skill is fully implemented.